During surgery, blood flows through extracorporeal circuits. The extracorporeal circuits include an oxygenation device to transfer oxygen to the blood received from the patient by means of a line which is known as venous line and then return it to the patient by means of a line known as arterial line.
The structure of the oxygenator is such as to delimit a portion of space which contains capillaries made of microporous membrane which convey oxygen and are wet externally by the blood that flows through this portion of space. There are also oxygenators which include a heat exchanger through which the blood is meant to flow before entering the oxygenator in order to be kept at the correct temperature.
Often on the arterial line there is a filter (the arterial filter), which is meant to retain any air bubbles present in the blood in order to prevent them from remaining in the blood that returns to the patient. However, this presence can be the source of problems for operators when one considers the inherent complexity of the extracorporeal circuit in which the arterial filter is introduced.